1. Field of the Invention
The invention relates generally to a simulation system for an automotive power plant, such as an internal combustion engine, for testing automotive components, such as an automatic power transmission. More specifically, the invention relates to an automotive power plant simulation system utilizing an electrically powered high inertia power plant, such as an electric motor, which is suitable for bench testing automotive components, such as an automatic power transmission.
2. Description of the Background Art
Japanese Patent First (unexamined) Publications (Tokkai) Showa 58-38833 and 61-53541 disclose bench testing systems for an automatic power transmission. In the disclosed system, an electric motor, a hydrostatic motor and so forth, are employed as substitute power plants in place of an automotive internal combustion engine. As can be appreciated, because of much higher inertia of the electric motor, hydrostatic motor and other substitute power plants in comparison with the automotive internal combustion engines, the substitute power plant is combined with speed increasing devices. Such automotive engine simulation system is useful for durability testing, static characteristics testing and so forth. However, due to the substantially high inertia moment, it is practically difficult to simulate transition characteristics at transmission speed ratio shifting and so forth. For instance, the electric motor has approximately 10 times higher inertia magnitude than that of the automotive engine.
For designing automatic power transmissions with enhanced shift feeling, reduced shift shock and so forth, it is essential to obtain data of the transition characteristics of power plant to be actually combined with the test transmission.
Therefore, Tokkai Showa 61-53541 as identified above, employs a strategy of a correction of command current for the electric motor. With the corrected command current, the output torque of the electric motor becomes substantially corresponding to the engine output torque to be output in response to a torque demand. Such an approach is generally successful in avoiding influence of high inertia of the high inertia power plant.
In the practical simulation, the automotive engine is simulated in terms of given parameters, such as an engine speed, a throttle valve open angle and so forth. Namely, in order to simulate the automotive engine transition characteristics for performing a bench test of an automatic power transmission, an engine speed and a throttle valve open angle are used as parameters for simulation. Therefore, an engine characteristics generator sets torque demand in terms of the engine speed indicative signal and a throttle valve open angle indicative signal to control the high inertia power plant, i.e. electric motor. When shift control parameters for controlling a shifting transmission gear ratio in the automatic power transmission is common to those used for simulating the engine characteristics, such approach is successfully introduced for performing a bench test. However, on the other hand, when the shift control parameters are different from those utilized for simulating the engine characteristics, difficulty is encountered in performing such as bench test. Therefore, it is desirable to provide a simulated engine characteristics generator which can perform a bench test of the automatic power transmissions irrespective of the shifting control parameters thereof.
On the other hand, in case that the shift control system of the automatic power transmission employs an intake air pressure as one of the shift control parameters, it becomes necessary to provide a simulated intake air pressure indicative data corresponding to the simulating condition of the engine.
Furthermore, in the modern and advanced automatic transmission technologies, a transmission gear ratio shifting pattern and/or shifting schedule is set and is variable depending upon various additional parameters. For instance, sometimes in the shift control system, it becomes necessary to provide data simulating an environmental condition, such as atmospheric pressure which is variable depending upon altitude. Since the intake air density to be introduced into the automotive engine is variable for causing a variation of the engine output characteristics, some of the environmental conditions also affect the engine output characteristics. Therefore, for such type of the automatic power transmission, it becomes essential to simulate engine characteristics with the environmental condition indicative parameter or parameters as simulation parameter or parameters.